Method for generating information to control the scanning beam of a display device

ABSTRACT

An enlarged photographic transparency of a print character to be displayed on a cathode ray tube is placed between a directional light source and a directional light detector aligned with the light source. Relative motion is introduced between the transparency and the aligned source and detector to form a vertical rectilinear scanning pattern across the transparency. Each subject print character is placed on the transparency between two reference characters that are in predetermined spatial relationship to the boundaries of the em square of the subject character. A series of binary indications corresponding to the elemental areas of the scanning pattern is produced from the response of the detector and stored on a first storage medium. Then, the indications representing the reference characters are sensed. From the indications representing the reference characters, the indications that represent the boundaries of the em squares of the subject characters are determined. Finally, the indications within the boundaries of the em squares of the subject characters are selectively transferred to a second storage medium. The subject characters are retrieved from the second storage medium as required to control the electron beam of the cathode ray tube.

United States Patent [1 1 Darnall Jan. 1, 1974 John C. Darnall, VanNuys, Calif.

[73] Assignee: The Times Mirror Company, Los

Angeles, Calif.

[22] Filed: Mar. 17, 1970 [21] Appl. No.: 20,320

[75] Inventor:

[5 7] ABSTRACT An enlarged photographic transparency of a printcharacter to be displayed on a cathode ray tube is placed between adirectional light source and a directional light detector aligned withthe light source. Relative motion is introduced between the transparencyand the aligned source and detector to form a vertical rectilinearscanning pattern across the transparency. Each subject print characteris placed on the transparency between two reference characters that arein pre- :2%; 3632;111:1111" 55. 5:.11????frf32fi3 to 9 58 Field 6:Search 315/18' 178/6.8 the 9"? the Subject. character' A 178/16 7 l EDIG 256/219 nary indications corresponding to the elemental areas of thescanning pattern is produced from the response [56] References Cited ofthe detector and stored on a first storage medium.

Then, the indications representing the reference char- UNITED STATESPATENTS acters are sensed. From the indications representing 3,436,4724/1969 Kyte 178/6.8 X the reference characters, the indications thatrepre- 3105384 9/1965 250/219 DD sent the boundaries of the em squaresof the subject 3,396,377 8/1963 Strout l78/6.8 X characters aredetermined Finally the i i i within the boundaries of the em squares ofthe subject 6/1969 Green et aL 178/73 x characters are selectivelytransferred to a secondstor- 3,260,887 7/1966 Alexander et al. 340/155DS age The Sublec characters are remeved from the second storage mediumas required to con- Primary Examiner BenJ-amin Padgett trol the electronbeam of the cathode ray tube. Assistant Examiner-.l. M. PotenzaAttorney-Christie, Parker & Hale 10 Claims 5 Drawing Figures COMfiZ/TEPCO/VTGOL /6 /0 2 3 /4 peopaC/NG 1C7/l/A/AR Amour/Ive ir'iiii l* 55%;;,fijggg FEAMM/G STORM/6 ggg 7P4A/5PAPE/VCV PMENTE JAN 1 m4 SHEEI 1 [1F 2PMENTED JAN 1 I974 SHEET 2 OF 2 Twxi T I METHOD FOR GENERATINGINFORMATION TO CONTROL THE SCANNING BEAM OF A DISPLAY DEVICE BACKGROUNDOF THE INVENTION This invention relates to the printing art and, moreparticularly, to the generation of information to control the scanningbeam of a display device in an electronic typesetting operation.

A recent development in the printing art is the use of a cathode raytube to electronically set type for newspapers and other printedmaterial. The page to be printed is displayed on the face of the cathoderay tube and photographically transferred therefrom to a plate coatedwith a photo-sensitive monomer. When the plate is developed, it istransformed into a printing plate, the areas exposed to light beingraised relative to the unexposed areas. For a process to reproduce suchprinting plates for multiple press operation, reference is made to mycopending US. Pat. application, Ser. No. 16,485, filed Mar. 4, 1970, andassigned to the assignee of the present application.

There are a number of commercially available cathode ray tubesspecifically designed for electronic typesetting. For the most part,these are sophisticated display devices having high resolution andcomplex electronic control circuitry. The scanning pattern of suchdisplay devices is substantially rectilinear due to the high resolutionand moves across the face of the cathode ray tube in successive verticalsweeps that correspond to the height of the line of type beingreproduced on the face of the cathode ray tube. The characterinformation for controlling the electron beam of the cathode ray tube isstored as binary indications in a memory and fed to the beam controlapparatus of the cathode ray tube by a programmed digital computer.

Attempts to generate the character information for controlling theelectron beam of the cathode ray tube by scanning techniques have provedunsuccessful. Presently, the character information is generated manuallyin the following way: A photographic transparency of the subjectcharacter is projected onto a screen to enlarge it. An artist draws theoutline of the subject character from the projection. The subjectcharacter is segmented into elemental areas by placing a grid over thecharacter outline. A human worker digitizes the character outline toconform to the lines of the grid. A key punch operator records thedigitized character outline on a storage medium, grid area by grid area,thereby producing a series of binary indications that represent thecharacter information in a form capable of reproducing the subjectcharacter on the face of a cathode ray tube.

It is also necessary to frame each character properly within its grid,i.e., to place the character in its proper location within the em squareallotted to such character. Otherwise, the characters displayed on theface of the cathode ray tube will not be arranged properly with respectto each other and the aesthetic effect of the character font will bediminished.

A substantial amount of human time and effort is required to generatethe binary beam control information representing even a single characterand to frame such character information properly within its em square.Most printing operations require thousands of characters. For example, atypical newspaper printing operation might require about ninetydifferent type fonts,

each in about three or four different sizes and each size having eightyor ninety characters. Thus, about thirtythousand different charactersare required in a typical newspaper printing operation.

SUMMARY OF THE INVENTION One aspect of the invention involves the use ofa directional light source and a directional light detector aligned withthe source to generate the information for controlling the electron beamof a cathode ray tube designed for electronic typesetting. First, thegraphic item to be displayed on the face of a cathode ray tube isproduced in enlarged form on a photographic transparency. Thetransparency is placed between the light source and the detector.Relative movement between the transparency and the aligned source anddetector is introduced to scan the transparency. Preferably, arectilinear vertical scanning pattern is employed. The indications ofthe detector responsive to the scanning of the transparency are storedon a storage medium as a source of information to control the electronbeam of a cathode ray tube. Preferably, these indications are in binaryform if the graphic item to be displayed on the face of the cathode raytube comprises a print character.

Another aspect of the invention involves framing the characterinformation generated in the manner described above properly within theem square of the character. A subject character is placed adjacent to areference character that is in predetermined spatial relationship to theboundaries of the em square of the subject character. The subject andreference characters are scanned together in the course of the samescanning pattern to produce a series of indications corresponding to theelemental areas of the scanning pattern. The indications representingthe reference character are sensed. From the indications representingthe reference character, the indications which represent the boundariesof the em square of the subject character are determined. Theindications representing the subject character are stored on a storagemedium for use to control the beam of a display device. Preferably, areference character is placed on both sides of each subject character sothe reference characters also define the width of the em square of thesubject character.

A feature of the framing aspect of the invention is the manner in whichthe series of indications corresponding to the elemental areas of thescan pattern is processed. First, the series of indications is stored ona first storage medium. After the boundaries of the em square of thesubject characters are determined, only the indications within theboundaries of the em squares of the subject characters areselectivelytransferred from the first medium to asecond storage medium,thereby eliminating the reference characters. The second storage mediumcomprises the source of character information for controlling the beamof the display device.

BRIEF DESCRIPTION OF THE DRAWINGS The features of a specific embodimentof the best mode contemplated of carrying out the invention areillustrated in the drawings, in which:

FIG. 1 is a block diagram depicting a method of gen erating characterinformation for controlling the electron beam of a cathode ray tube toelectronically typeset a page to be printed.

FIGS. 2 and 3 are a side elevation view and a section view,respectively, of apparatus for carrying out a rectilinear optical scanin accordance with the method depicted in FIG. 1.

FIG. 4 is a block diagram of the individual steps of the framingoperation depicted in the method of FIG. 1.

FIG. 5 is a diagram depicting several subject and reference charactersplaced in a predetermined spatial relationship to each other.

DETAILED DESCRIPTION OF THE SPECIFIC EMBODIMENT The blocks in FIG. 1represent the steps involved in generating character information forcontrolling the electron beam of a cathode ray tube to display on itsface print characters. Block represents the step of producing anenlargement of one or more print characters on a photographictransparency. Block 11 represents the step of optically scanning thetransparency in a rectilinear, preferably vertical, scanning pattern.This scanning step is discussed in more detail below in connection withFIGS. 2 and 3. Block 12 represents the step of producing a series ofbinary indications corresponding to the successive elemental areas ofthe scanning pattern. Typically, these binary indications would beproduced by periodically sampling the output of a light detector that ispart of the optical scanning equipment. If the output of the lightdetector falls below a threshold level, one binary value is indicated,and if it lies above the threshold level, the other binary value isindicated. Block 13 represents the step of framing each character withinits em square, i.e., determining which binary indications represent theboundaries of the em square of each character. The framing step isdescribed in detail below in connection with FIGS. 4 and 5. Block 14represents the step of storing the binary indications corresponding tothe framed characters. Block 15 represents the step of displayingcharacters on a cathode ray tube, the electron beam of which iscontrolled by the stored binary indications. As represented by a bracket16, the steps represented by blocks 12 through 15 can be carried outunder the control of a programmed digital computer. Steps 12 through 15are per se old to the art. The invention involves the production of thebinary indications by optically scanning an enlarged photographictransparency of the characters and the particular manner of framing thecharacters within their em squares.

Reference is now made to FIGS. 2 and 3 for a description of apparatusthat scans the enlarged photographic transparency. The degree ofenlargement depends upon the difference in size of the elementalscanning areas of the optical scanning pattern represented by block 11and the electron beam scanning pattern represented by block 15 andfurther depends upon the size in which the character is to be displayedon the cathode ray tube. A hollow cylindrical drum is supported by arotatable shaft 21. During the scanning operation, shaft 21 is driven bya motor, not shown, at a constant angular velocity. Drum 20 has a narrowrectangular slot 22 and a wide rectangular slot 23. A carriage 24 ismounted on a frame 25 to translate in a direction parallel to the axisabout which drum 20 rotates. A directional light source 26 is mounted onone arm of carriage 24, which lies outside drum 20, and a directionallight detector 27, such as a photocell, is

mounted on the other arm of carriage 24, which is located inside drum20. Source 26 and detector 27 are aligned with each other so light iscoupled from source 26 to detector 27 in the absence of opacity in thepath between them. A revolution detector 30 is coupled to shaft 21. Eachtime shaft 21 makes a revolution. detetor 30 produces a pulse thatactuates a stepping mechanism 31. Stepping mechanism 31 is coupled tocarriage 24. Accordingly, after each revolution of drum 20, source 26and detector 27 are advanced as a unit a discrete distance to the right,as viewed in FIG. 2. A photographic transparency 32 bearing the printcharacter or characters to be scanned is mounted over slot 23. As drum20 rotates, source 26 and detector 27 scan transparency 32 in successiveparallel semicircular sweeps, each of which lies in a planeperpendicular to the axis of drum 20.

The characters are oriented on transparency 32 so that they are readablewith drum 20 in the position shown in FIG. 2. Thus, the scan patterntraverses the characters in rectilinear, vertical sweeps displacedsuccessively from each other, moving from left to right. The output ofdetector 27 varies, depending upon whether the area of transparency 32in the path of source 26 at any given moment is opaque or translucent. Aseries of periodic sampling pulses are produced in synchronism with therotation of drum 20. The output of detector 27 is sampled responsive toeach pulse. If the sample of the output of detector 27 is above aparticular threshold level, a first binary value is indicated, and if itis below the threshold level, a second binary value is indicated. Thus,for each rotation of drum 20, a series of binary indications areproduced equal in number to the number of sampling pulses produced perrevolution of drum 20. A first segment of this series of binaryindications, corresponding to the rotation of slot 22 between source 26and detector 27, are all of the first binary value. A second segment ofthis series, corresponding to the rotation of slot 23 between source 26and detector 27, vary between the first binary value and the secondbinary value depending upon the nature of the characters on transparency32. These are the binary indications of interest. A third segment ofthis series, corresponding to the rotation of the small portion of drum20 separating slots 22 and 23 between source 26 and detector 27, are allof the second binary value. A fourth segment of this series,corresponding to the rotation of the remainder of drum 20 between source26 and detector 27 are all of the second binary value. Revolutiondetector 30 is adjusted to actuate stepping mechanism 31 immediatelyprior to the passage of slot 22 between source 26 and detector 27. Thus,the first segment of each series of indications serves as a marker todesignate the beginning of each vertical sweep. This marker can be usedto set the electronic reading circuitry associated with detector 27 andto indicate the beginning of the second segment in the course ofprocessing the binary indications produced from detector 27. Since theportion of drum 20 separating slots 22 and 23 has a known constant arc,a given number of sampling pulses always occur between the end of thefirst segment of binary indications and the beginning of the secondsegment of binary indications. The number of sampling pulses producedper revolution of drum 20 and the amount that carriage 24 is advancedeach revolution determine the size of the elemental areas of thescanning pattern. One binary indication represents each such elementalarea.

Optical scanning of the characters in the manner shown in FIGS. 2 and 3produces electron beam controlling character information of high qualitywithout appreciable manual labor. Human intervention is only required tomount the transparencies on drum 20 and to start the drive motor fordrum 20. A digital computer can be programmed to process the output ofdetector 27 via an analog-to-digital converter.

As used in this specification, the term em square means the spaceallotted to a particular character. The vertical height of the emsquares of the characters in any one font and size are identical but thehorizontal width of such em squares vary from character to character.For example, a W has a wider em square than an I. A difficultyassociated with scanning the characters is the framing of the characterswithin their respective em squares, in other words, determining whichbinary indications in the series of vertical sweeps represent theboundaries of the em square of each character. It is essential to thedisplay of the characters in their proper spatial relationship to eachother on the cathode ray tube that the characters be properly framedwithin their respective em squares.

The invention accomplishes framing by placing on either side of eachcharacter to be scanned, hereafter called a subject character, areference character that is in predetermined spatial relationship to theboundaries of the em square of the subject character. Specimens of allthe characters of a type font in their proper relative spatialrelationship are readily available from designers of printing type. Inordering these specimens, it is simply necessary to specify that someselected reference character be placed on either side of each subjectcharacter in the font in its proper relative spatial relationship.

Reference is made to FIG. 5, in which an upper case G, a lower case g,and three reference characters are shown. A simplified I is selected asthe reference character for ease of detection. In principle, any otherunique, detectable symbol could be selected as the reference character.As depicted in FIG. 5, one reference character that lies between twosubject characters can help to frame both of these subject characters.In other words,it is not necessary to have four reference characters toframe two adjacent subject characters; three reference characters willsuffice, one being shared by both subject characters. The gridsuperimposed upon the characters in FIG. 5 represents the elementalareas of the scanning pattern. In other words, the areas of the gridscorrespond to the binary representations, a black area being one binaryvalue and a white area being the other binary value. In practice, manymore elemental areas would be employed than are actually shown in FIG.5. The heavy lines surrounding each character represent the boundariesof the em square of such character. Only the elemental areas inside theboundaries of the em squares are represented. For the purpose ofillustration, it is assumed that the optical scanning beam starts fromthe lower lefthand corner in FIG. 5, and moves upward from elementalarea to elemental area in successive vertical sweeps that progress fromleft to right. The number of elemental areas from the edges of areference character to the boundaries of its em square are known. Asrepresented in FIG. 5, the number of elemental areas from the top edgeof the reference character to the top boundary of its em square is Y thenumber of elemental areas from the bottom edge of the referencecharacter to the bottom boundary of its em square is Y the number ofelemental areas from the right edge of the reference character to theright side boundary of its em square is X and the number of elementalareas from the left edge of the reference character to its left sideboundary is X It can be seen from FIG. 5 that the top boundary of the emsquares of the reference characters is also the top boundary of the emsquares of the subject char acters, e.g. the upper case G and the lowercase g, the lower boundary of the em squares of the reference charactersis also the lower boundary of the em squares of the subject characters,the righthand boundary of the em square of each reference character isthe lefthand boundary of the em squares of the adjacent subjectcharacter, and the lefthand boundary of the em square of each referencecharacter is also the righthand boundary of the em square of theadjacent subject character. In short, the boundaries of the em square ofeach subject character are defined by the em square boundaries of theadjacent reference characters which are known from the position of suchreference characters.

One way in which the boundaries of the em squares of the subjectcharacters can be determined from the position of the adjacent referencecharacters is as follows: Count the number of elemental areas, Y fromthe beginning of the second segment to the lower edge of the referencecharacter. Subtract Y from Y to find the number of elemental areas fromthe beginning of the second segment to the lower boundary of the emsquare of the subject character on each vertical sweep. Add Y Y, (thenumber of elemental areas in the length of the reference character), andY to find the number of elemental areas from the beginning of the secondsegment to the upper boundary of the em square of the subject characteron each vertical sweep. Count a number of vertical sweeps X from theright edge of the lefthand adjacent reference character to find whichvertical sweep is the lefthand boundary of the em square of the subjectcharacter. Count a number of vertical sweeps X from the left edge of therighthand adjacent reference character to find which vertical sweep isthe righthand boundary of the em square of the subject character. Onlythe series of binary indications for those vertical sweeps between thevertical boundaries of the em square of the subject character thusdetermined are used as the character information. Further, within suchseries, only those binary indications between the horizontal boundariesof the em square of the subject character thus determined are used asthe character information.

FIG. 4 represents the steps involved in framing the subject charactersin their respective em squares. As represented by a block 40, the seriesof binary indications derived from the output of detector 27 are storedon a first storage medium, such as magnetic tape. These binaryindications represent both the subject characters and the referencecharacters. As represented by a block 41, the reference charactersstored on the first storage medium are sensed. As represented by a block42, the boundaries of the em square of each subject character are thenlocated by means of the reference characters in the manner described inthe preceding paragraph or in some other manner. As represented by ablock 43, the subject characters are selectively transferred to a secondstorage medium; in other words, only the binary indications lyingbetween the boundaries of the em squares of the subject characters aretransferred to the second storage medium. The second medium serves as asource of beam controlling character information for the cathode raytube. The framing operation could be carried out with a programmeddigital computer or by hand. In the latter case, the first storagemedium could be a paper printout on which the series of binaryindications derived from the output of detector 27 are visible to ahuman being. The reference characters are sensed by visually observingwhere its edges are located in the series of binary indications and theboundaries of the em square of each subject character are located bymanually counting the binary indications in the manner described in thepreceding paragraph. The binary indications within the boundaries of theem square of each character could then be put into an electronic memoryby a key punch operator.

The described embodiment of the invention is only considered to bepreferred and illustrative of the inventive concept; the scope of theinvention is not to be restricted to such embodiment. Various andnumerous other arrangements may be devised by one skilled in the artwithout departing from the spirit and scope of this invention. Forexample, the optical scan could also be employed to generate electronbeam control information concerning pictorial material, in which casethe output of detector 27 would be converted into a multiple digit codeinstead of binary indications. Further, it would be possible to use onereference character to frame a subject character, instead of two, if thewidths of the em squares were for some reason either known or constant.

What is claimed is: l. A method for displaying graphic information onthe face of a cathode ray tube having an electron beam, the methodcomprising the steps of:

producing the information to be displayed on a photographic transparencyby placing a subject print character adjacent to a reference characterthat is in predetermined spatial relationship to the boundaries of theem square of the subject character;

placing the transparency between a point source of light and a pointdetector of light aligned with each other;

introducing relative movement between the transparency and the alignedpoint source and detector to scan the subject and reference characterson the transparency together;

storing the indications of the detector responsive to the scanning ofthe transparency; and

controlling the electron beam of the cathode ray tube responsive to thestored indications so as to reproduce on the face of the cathode raytube the subject print character on the transparency.

2. The method of claim 1, in which the step of introducing relativemovement between the transparency and the aligned point source anddetector comprises the steps of:

mounting the transparency over a slot on a rotating drum;

placing the light source and light detector on opposite sides of thedrum; and

translating the light source and detector as a unit parallel to the axisof rotation of the drum a discrete distance after each revolution of thedrum.

3. A method of generating character information for controlling theelectron beam of a cathode ray tube to display on its face printcharacters, the method comprising the steps of:

producing an enlarged photographic transparency of the character to bedisplayed and reference marks in predetermined spatial relationship tothe boundaries of the em square of the character to be displayed;

aligning a directional light source and a directional light detector soas to couple light to the detector in the absence of opacity between thesource and the detector;

introducing relative motion between the transparency and the alignedsource and detector so as to scan together the character to be displayedand the reference marks on the transparency;

producing binary indications representative of the character and thereference marks responsive to the detector while the transparency isbeing scanned; and

storing the binary indications for the control of the electron beam.

4. A method for generating character information to control the scanningbeam of a print character display device, the method comprising thesteps of:

placing a subject character adjacent to a reference character that is inpredetermined spatial relationship to the boundaries of the em square ofthe subject character; scanning the subject and reference characterstogether to produce a series of indications corresponding to theelements of scanning pattern;

sensing the indications representing the reference character;

determining which indications represent the boundaries of the em squareof the subject character from the indications representing the referencecharacter; and

storing the indications representing the subject character.

5. A method for generating print character information to control thebeam of a print character display device, the method comprising thesteps of:

placing a plurality of characters to be generated on a printing mediumin their proper spatial relationship to each other; placing on bothsides of each character to be generated two reference characters thatare in predetermined spatial relationship to the boundaries of the emsquare of such character to be generated;

scanning the reference characters and the characters to be generatedtogether to produce a series of indications corresponding to theelemental areas covered by such scanning;

storing the series of indications on a first storage medium; sensingthose indications of the series stored on the first medium representingthe reference characters;

determining from the indications representing the reference characterswhich indications represent the boundaries of the em square of eachcharacter to be generated; and

transferring from the first medium to a second storage medium only theindications within the boundaries of the em squares of the characters tobe generated.

6. The method of claim 5, in which the printing medium comprises anenlarged photographic transparency of the characters to be generated andthe reference characters, and the step of scanning the referencecharacters and the characters to be generated comprises the steps of:

mounting the transparency over a slot on a rotating placing the lightsource and light detector on opposite sides of the drum; and

translating the light source and detector as a unit parallel to the axisof rotation of the drum a discrete distance after each revolution of thedrum.

7. A method for displaying graphic information on the face of a cathoderay tube having an electron beam, the method comprising the steps of:

producing an enlarged photographic transparency of the character to bedisplayed; mounting the transparency over a slot on a rotating drum; i

aligning a directional light source and a directional light detector onopposite sides of the drum so as to couple light to the detector in theabsence of opacity between the source and the detector;

translating the light source and detector as a unit parallel to the axisof rotation of the drum a discrete distance after each revolution of thedrum;

producing binary indications representative of the character responsiveto the detector while the transparency is being scanned;

storing the binary indications; and

controlling the electron beam of the cathode ray tube responsive to thestored binary indications so as to reproduce on the face of the cathoderay tube the character to be displayed.

8. A method for generating character information to control the scanningbeam of a print character display device, the method comprising thesteps of:

placing a character to be generated on a printing medium;

placing on both sides of the character to be generated two uniquereference characters that are in predetermined spatial relationship tothe boundaries of the em square of the character to be generated;

scanning the character to be generated and the reference characterstogether to produce a series of indications corresponding to theelements of the scan;

sensing the indications representing the reference characters;

determining from the indications representing the reference characterswhich indications represent the boundaries of the em square of thecharacter to be generated; and

storing the indications representing the character to be generated forthe control of the scanning beam of the display device.

9. A method for displaying print characters on the face of a printcharacter display device, the method comprising the steps of:

placing a plurality of subject characters and unique referencecharacters in a row in proper spatial relationship to one another,reference characters being located at both ends of the row andalternating with subject characters between the ends of the row;scanning the subject and reference characters together to produce aseries of binary indications corresponding to the elements of the scan;

sensing the binary indications representing the reference characters;

determining which indications represent the bounda ries of the emsquares of the subject characters from the binary indicationsrepresenting the reference characters;

storing the binary indications representing the subject characters; and

controlling the scanning beam of the display device responsive to thestored binary indications so as to reproduce on the face of the displaydevice the subject characters.

10. The method of claim 5, in which one reference character serves todetermine in part the boundaries of the em squares of the characters tobe generated on both sides of such reference character.

saw-Ln UNITED STATES PATENT OFFICE a 569) CERTIFECATE or CQRREQTMNPatent No. 3,783,331 Dated January 1, 1974 Invantofls) JOHN NALL It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

I" '7 Column 1, line 18, delete "For a process to reproduce such";

lines 19 through 22, delete in their entirety.

Column 8, line 37, between "of" and "scanning" insert -a--.

Column 10, line 19, between "device" and the comma insert --having acontrollable seaming beam--.

Signed and sealed this 29th day of October 1974.

(SEAL) Attest:

MCCOY M. GIBSON JR. c. MARSHALL DANN Attesting Officer Commissioner ofPatents 67:8Q-L'lR l t Y UNITED STATES PATENT OFFICE l V CERTIFICATE OFCORRECTION Patent No. 3,783,331 Dated January 1 1974 JOHN c. DARNALLInvontofls) It is certified: that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

r-1 Column 1, line 18, delete "For a process to reproduce such";

lines 19 through 22, delete in their entirety.

Column 8, line 37, between "of" and "scanning" insert --a--. Column 10,line 19, between "device" and the comma insert having a controllablescarming beam--.

Signed and "sealed this 29th day of October- 1974.;

(SEAL) 1 Attest: r I 'uccor M. GIBSON JR. c. MARSHALL DANN AttestingOfficer Commissioner of Patents

1. A method for displaying graphic information on the face of a cathoderay tube having an electron beam, the method comprising the steps of:producing the information to be displayed on a photographic transparencyby placing a subject print character adjacent to a reference characterthat is in predetermined spatial relationship to the boundaries of theem square of the subject character; placing the transparency between apoint source of light and a point detector of light aligned with eachother; introducing relative movement between the transparency and thealigned point source and detector to scan the subject and referencecharacters on the transparency together; storing the indications of thedetector responsive to the scanning of the transparency; and controllingthe electron beam of the cathode ray tube responsive to the storedindications so as to reproduce on the face of the cathode ray tube thesubject print character on the transparency.
 2. The method of claim 1,in which the step of introducing relative movement between thetransparency and the aligned point source and detector comprises thesteps of: mounting the transparency over a slot on a rotating drum;placing the light source and light detector on opposite sides of thedrum; and translating the light source and detector as a unit parallelto the axis of rotation of the drum a discrete distance after eachrevolution of the drum.
 3. A method of generating character informationfor controlling the electron beam of a cathode ray tube to display onits face print characters, the method comprising the steps of: producingan enlarged photographic transparency of the character to be displayedand reference marks in predetermined spatial relationship to theboundaries of the em square of the character to be displayed; aligning adirectional light source and a directional light detector so as tocouple light to the detector in the absence of opacity between thesource and the detector; introducing relative motion between thetransparency and the aligned source and detector so as to scan togetherthe character to be displayed and the reference marks on thetransparency; producing binary indications representative of thecharacter and the reference marks responsive to the detector while thetransparency is being scanned; and storing the binary indications forthe control of the electron beam.
 4. A method for generating characterinformation to control the scanning beam of a print character displaydevice, the method comprising the steps of: placing a subject characteradjacent to a reference character that is in predetermined spatialrelationship to the boundaries of the em square of the subjectcharacter; scanning the subject and reference characters together toproduce a series of indications corresponding to the elements ofscanning pattern; sensing the indications representing the referencecharacter; determining which indications represent the boundaries of theem square of the subject character from the indications representing thereference character; and storing the indications representing thesubject character.
 5. A method for generating print characterinformation to control thE beam of a print character display device, themethod comprising the steps of: placing a plurality of characters to begenerated on a printing medium in their proper spatial relationship toeach other; placing on both sides of each character to be generated tworeference characters that are in predetermined spatial relationship tothe boundaries of the em square of such character to be generated;scanning the reference characters and the characters to be generatedtogether to produce a series of indications corresponding to theelemental areas covered by such scanning; storing the series ofindications on a first storage medium; sensing those indications of theseries stored on the first medium representing the reference characters;determining from the indications representing the reference characterswhich indications represent the boundaries of the em square of eachcharacter to be generated; and transferring from the first medium to asecond storage medium only the indications within the boundaries of theem squares of the characters to be generated.
 6. The method of claim 5,in which the printing medium comprises an enlarged photographictransparency of the characters to be generated and the referencecharacters, and the step of scanning the reference characters and thecharacters to be generated comprises the steps of: mounting thetransparency over a slot on a rotating drum; placing the light sourceand light detector on opposite sides of the drum; and translating thelight source and detector as a unit parallel to the axis of rotation ofthe drum a discrete distance after each revolution of the drum.
 7. Amethod for displaying graphic information on the face of a cathode raytube having an electron beam, the method comprising the steps of:producing an enlarged photographic transparency of the character to bedisplayed; mounting the transparency over a slot on a rotating drum;aligning a directional light source and a directional light detector onopposite sides of the drum so as to couple light to the detector in theabsence of opacity between the source and the detector; translating thelight source and detector as a unit parallel to the axis of rotation ofthe drum a discrete distance after each revolution of the drum;producing binary indications representative of the character responsiveto the detector while the transparency is being scanned; storing thebinary indications; and controlling the electron beam of the cathode raytube responsive to the stored binary indications so as to reproduce onthe face of the cathode ray tube the character to be displayed.
 8. Amethod for generating character information to control the scanning beamof a print character display device, the method comprising the steps of:placing a character to be generated on a printing medium; placing onboth sides of the character to be generated two unique referencecharacters that are in predetermined spatial relationship to theboundaries of the em square of the character to be generated; scanningthe character to be generated and the reference characters together toproduce a series of indications corresponding to the elements of thescan; sensing the indications representing the reference characters;determining from the indications representing the reference characterswhich indications represent the boundaries of the em square of thecharacter to be generated; and storing the indications representing thecharacter to be generated for the control of the scanning beam of thedisplay device.
 9. A method for displaying print characters on the faceof a print character display device having a controllable scanning beam,the method comprising the steps of: placing a plurality of subjectcharacters and unique reference characters in a row in proper spatialrelationship to one another, reference characters being located at bothends of the row and alternating wIth subject characters between the endsof the row; scanning the subject and reference characters together toproduce a series of binary indications corresponding to the elements ofthe scan; sensing the binary indications representing the referencecharacters; determining which indications represent the boundaries ofthe em squares of the subject characters from the binary indicationsrepresenting the reference characters; storing the binary indicationsrepresenting the subject characters; and controlling the scanning beamof the display device responsive to the stored binary indications so asto reproduce on the face of the display device the subject characters.10. The method of claim 5, in which one reference character serves todetermine in part the boundaries of the em squares of the characters tobe generated on both sides of such reference character.